1) Remove UE Context Release Response code: there is no
such thing in the specs, it is either UE Context Release Request
(NG-RAN node initiated) or UE Context Release (AMF initiated)
(3GPP TS 38.413). The former message has only the request, no
response is defined by the specs. The code in the stack had no
purpose at all and was removed.
2) The UE Context Release Request message only contains a PDU
Session Resource List (optional) of PDU Session IDs, therefore
the use of pdusession_release_t was wrong and was refactored
This commit completes the NGAP Mobility Management procedure for N2 handover.
Upon failure on source gNB the Handover Cancel message is sent to the AMF which
in return responds with an ack.
According to 4.9.1.3.3 of 3GPP TS 23.502:
> 2a. - 2c. The S-RAN sends the Uplink RAN Status Transfer message to the S-AMF,
> as specified in TS 36.300 [46] and TS 38.300 [9]. The S-RAN may omit sending
> this message if none of the radio bearers of the UE shall be treated with PDCP status preservation.
TS 38.300 says:
> For DRBs not configured with DAPS, the source gNB sends the SN STATUS TRANSFER message to the target
> gNB to convey the uplink PDCP SN receiver status and the downlink PDCP SN transmitter status of DRBs for
> which PDCP status preservation applies (i.e. for RLC AM). The uplink PDCP SN receiver status includes at
> least the PDCP SN of the first missing UL PDCP SDU and may include a bit map of the receive status of the out
> of sequence UL PDCP SDUs that the UE needs to retransmit in the target cell, if any. The downlink PDCP SN
> transmitter status indicates the next PDCP SN that the target gNB shall assign to new PDCP SDUs, not having a
> PDCP SN yet.
i.e., for DRBs for which PDCP status preservation applies (i.e. for RLC AM), which is is our case.
This commit introduces full support for NG-RAN Status Transfer message handling
(TS 38.413 §9.2.3.13-14) in CU. It enables correct state transfer of PDCP COUNT
values (SN + HFN) during mobility or recovery scenarios.
Summary of changes - NGAP:
* Added encoding/decoding support for UL/DL RAN Status Transfer message
* Defined structures for: ngap_drb_count_value_t, ngap_drb_status_t,
ngap_ran_status_container_t, ngap_ran_status_transfer_t
This commit introduces the NG Mobility Management Procedure known as
Handover Notification. The outbound message is sent by the target NG-RAN
and is known as Handover Notify. The procedure is used to indicate to
the AMF that the UE has arrived to the target cell and the NG-based
handover has been successfully completed
* after RRCReconfiguration complete, in the N2 callback for HO success
* add NGAP encoder for the message
* RRC callback to trigger Handover Notify message
Co-authored-by: batuhan duyuler <batuhan.duyuler@firecell.io>
* add NG Handover Command message decoder
* process in RRC: encode RRCReconfiguration message
from the received HandoverCommandMessage
* trigger RRCReconfiguration for handover
Co-authored-by: batuhan duyuler <batuhan.duyuler@firecell.io>
This commit completes the NG Mobility Management Procedure known as
Handover Resource Allocation. The outbound message is sent by the
target NG-RAN and is known as Handover Request Acknowledge.
Major changes:
* add RRC callback to trigger the generation of NG Handover
Request Acknowledge on the target NG-RAN
* add NG Handover Request Acknowledge encoder
Co-authored-by: batuhan duyuler <batuhan.duyuler@firecell.io>
This commit introduces the NG Mobility Management Procedure known as
Handover Resource Allocation. The inbound message is sent by the AMF
and is known as Handover Request.
Major changes:
(0) Add Handover Resource Allocation initiating message decoding
* add case for NGAP initiating message and unsuccessful message decoding
(1) handle Handover Request on the target NG-RAN
(2) decode NG Handover Request message
(3) process payload, e.g. create UE context,
store IDs, set UP security and trigger bearer setup
Co-authored-by: batuhan duyuler <batuhan.duyuler@firecell.io>
This message is sent from the Target NG-RAN to the AMF.
The commit introduces:
* NGAP encoding function
* N2 callback for the target gNB
* handle the failure in RRC, inform NGAP
* send NGAP message to AMF via SCTP
Note: UE context in NGAP is fetched from the amf_ue_ngap_id
Co-authored-by: batuhan duyuler <batuhan.duyuler@firecell.io>
This commit introduces the NG Mobility Management Procedure known as
Handover Preparation. The outbound message is sent by the source NG-RAN
and is known as Handover Required.
* introduce NGAP library for Mobility Management
* introduce NGAP IEs encoder functions for Handover Required and relevant common IEs
* handle RRC trigger in NGAP and Send NGAP Handover Required to the AMF
Co-authored-by: batuhan duyuler <batuhan.duyuler@firecell.io>
* Remove drb_is_active: function is unused and the logic will be later
added to another function to add DRBs if necessary
* Remove unused NGAP structs and empty TODO functions
* Remove unused pdusession_setup_req_t struct definition
Guido Casati